Question: code for tri diagonal matrix

I want to make tridaigonal matrix like this for n x m order

[3  2  0  0  0  0]

[1  3  1  0  0  0]

[0  1  3  1  0  0]

[0  0  1  3  1  0]

[0  0  0  1  3  1]

[0  0  0  0  2  3]

please help me how to write it in maple

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